This invention relates to protective coatings for food products. More particularly, it relates to a method of preparing and using a protective coating for food products such as fruits, vegetables and nuts, based on chitosan or chitosan derivatives, and to the coating composition itself.
It is well known to coat food products, such as fruits, vegetables and nuts, to protect them against mold, rot and water damage and to improve their appearance and, hence, their marketability. Common coatings now in use employ proteins, gums, resins, hydrocolloids, waxes, and oils either alone or in combination, to achieve certain desired objectives. Enhancing appearance, slowing moisture loss, affecting the respiration or ripening process of fruits, nuts, and vegetables, are several of the goals of many modern food coatings.
Coating fruit, first with a sorbate and then with a wax, is disclosed by U.S. Pat. No. 4,434,184, granted Feb. 28, 1984 to Paul M. Nelson.
Coating food products with a shellac based coating is disclosed by U.S. Pat. No. 4,810,434, granted Mar. 7, 1989, to Jonathan Seaborne and David C. Igberg.
U.S. Pat. No. 5,554,445, granted Sep. 10, 1996, to Henryk Struszczyk and Olli Kivekxc3xa4s, discloses encapsulation of seeds by a film of microcrystalline chitosan.
U.S. Pat. No. 5,283,064, granted Feb. 1, 1994, to Tsutomu Suzuki; Kenichi Hashiudo; Takayuki Matsumoto; Toshihiro Higashide and Takeru Fujii discloses making a capsule that is composed of chitosan; U.S. Pat. No. 2,040,880, granted May 19, 1936, to George W. Rigby, discloses making a then film product from deacetylated chitin. U.S. Pat. Nos. 2,040,880, 5,283,064, and 5,554,445 are non-analogize art to the subject invention.
An object of the present invention is to provide a new and improved coating and a method of preparing and using the coating.
Another object of the present invention is to provide a coating composition that is easy to manufacture and apply.
The present invention utilizes atypical properties of chitosan (at biological pH values, chitosan is positively charged) to provide an improved coating film for food products, such as fruits, vegetables and nuts that is easy to apply.
The protective coatings of the present invention are edible and are for use with fruits, vegetables, and nuts. It is made by admixing a chitosan polymer to an acid and water solution in an amount and molecular weight sufficient to form an edible composition having a solid content greater than 5% and a liquid viscosity. The composition is applied to a food product to provide an edible protective coating for the food product.
According to one aspect of the invention, a chitosan preparation is formed from a partially hydrolyzed virgin chitosan to lower the molecular weight of the polymer. The chitosan polymer is hydrolyzed to a molecular weight low enough that a gel will not be formed when it is admixed to the acid and water solution. Acetic acid is particularly suitable for making the acid and water solution.
According to another aspect of the invention, a nonionic carnauba wax emulsion is added to the composition before the composition is applied to the food product. Preferably, a chitosan polymer is used having a molecular weight sufficient to form a composition with the acid and water solution in which the solids content is about 15% or higher.
Additional additives to the composition may include, but are not limited to a preservative, e.g. sodium benzoate, in an amount sufficient to extend the useful working life of the composition; and additive, e.g. zinc acetate, for enhancing adhesion of the protective coating to the food product; a wetting agent; and additives that improve physical characteristics of the protective coating, including proteins, carbohydrates, other hydrocolloids, resins, gums, oils, natural or synthetic waxes and/or lipids. These additives may be used alone or in combination.
The present invention provides an alternative to existing and conventional coatings for food products such as fruits, vegetables and nuts. The invention includes producing a high solids solution of water, acetic acid (or other acid), and a selectively engineered molecular weight range of chitosan or chitosan derivatives. This solution may be used by itself, as the coating, or some other coating enhancers can be added to and made apart of the solution before it is used. The solution is applied to food products such as fruit, vegetables or nuts by use of conventional equipment and coating techniques. The solution is applied and then the food product is dried, also by use of conventional equipment and techniques.
The invention includes providing a protective coating for fruits, vegetables: and nuts that is basically characterized by an acetic acid water solution to which chitosan or selected hydrolysates of chitosan have been admixed in an amount sufficient to produce an edible coating that protects the food product from water loss or water damage, increases shelf life, improves the appearance of the product, and protects the product, all resulting in improved marketability of the product.
Chitosan is partially or completely deacetylated chitin. According to one aspect of the invention, the preferred chitosan polymer is of a molecular weight range that results in the formation of a lower viscosity liquid as opposed to a gel when unmodified chitosan is admixed with a water acid solution. According to the invention, in the manufacture of the chitosan from the chitin, the chitosan is hydrolyzed chemically or any other way that is currently know or is yet to be developed, to lower the molecular weight of the polymer.
The invention further includes preparing a solution of water, acetic acid (or other acid) and chitosan or chitosan derivatives, alone or with other additives and then either dipping the food product in this solution, or by brushing or spraying the solution on the food product, to form the protective coating.
Other objects, advantages and features of the invention will become apparent from the description of the best mode set forth below, from the drawings, from the claims and from the principles that are embodied in the specific structures that are illustrated and described.